PHPMySQL: How to determine if value already exists in database - php

Question

I have a form button that I need to do two different things, based on user input and whether that input already exists in my database. If the input DOES NOT exist, then the button will create a new record. If it DOES exist, then the existing record will be updated.
Here's my PDO query as it stands now:
/* First, we need to discover whether the Proposal No. entered already exists in the
database. If it doesn't, then a new record will be created. If
it does, then an existing record will be updated. */
$pNoExists = $con->prepare("SELECT ProposalNo FROM ptfp1");
$pNoExists->execute();
$row = $pNoExists->fetch(PDO::FETCH_ASSOC);
When I run $row = $pNoExists->fetch(PDO::FETCH_ASSOC); through a while loop, all of the values for the field are present. Now I just need some guidance on how to use that in my button setup. This is what I want to do:
if($_POST['ButtonPush'] && input doesn't exist) {
Create new record;
}
else {
Update existing record;
}
Simple, right? But it's eluding me.

Answer 1

Given what you have, I would do:
if($_POST['ButtonPush'] && array_search($all_values, $input_value)) {
Create new
}
else {
Update
}
However, like the comment above, you may want to simply add a where clause to your "SELECT" statement so you are not grabbing the entire database table contents every time. And, one could even convert the SELECT in to a SELECT COUNT to bring down the amount of data being requested.

Answer 2

You could use SELECT count(*) FROM ptfp1 WHERE ProposalNo = :input
Than check if the value you get is bigger than one. If it is, update it:
UPDATE ptfp1 set ... where ProposalNo = :input
else
INSERT INTO ptfp1(...) VALUES (...)

Answer 3

Assuming ProposalNo has a unique index in the table, you can do it all in one query:
INSERT INTO ptfp1 (ProposalNo, colA, colB, colC, ...)
VALUES (:ProposalNo, :colA, :colB, :colC, ...)
ON DUPLICATE KEY
UPDATE colA = VALUES(colA), colB = VALUES(colB), colC = VALUES(colC), ...
Documentation

Answer 4

Figured out an answer. Just use the user's input (stored in a session variable) in my SELECT statement:
$pNoExists = $con->prepare("SELECT ProposalNo FROM ptfp1 WHERE ProposalNo =
'".$_SESSION['ProposalNo']."'");
$pNoExists->execute();
$row = $pNoExists->fetch(PDO::FETCH_ASSOC);
And the button:
if($_POST['ButtonPush'] && !$row['ProposalNo']) {
Write new record;
}
else {
Update existing record;
}
Hiding in plain sight!